1 /* atof_vax.c - turn a Flonum into a VAX floating point number
2 Copyright (C) 1987-2024 Free Software Foundation, Inc.
3
4 This file is part of GAS, the GNU Assembler.
5
6 GAS is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GAS is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GAS; see the file COPYING. If not, write to the Free
18 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
19 02110-1301, USA. */
20
21 #include "as.h"
22
23 /* Precision in LittleNums. */
24 #define MAX_PRECISION 8
25 #define H_PRECISION 8
26 #define G_PRECISION 4
27 #define D_PRECISION 4
28 #define F_PRECISION 2
29
30 /* Length in LittleNums of guard bits. */
31 #define GUARD 2
32
33 int flonum_gen2vax (int, FLONUM_TYPE *, LITTLENUM_TYPE *);
34
35 /* Number of chars in flonum type 'letter'. */
36
37 static unsigned int
atof_vax_sizeof(int letter)38 atof_vax_sizeof (int letter)
39 {
40 int return_value;
41
42 /* Permitting uppercase letters is probably a bad idea.
43 Please use only lower-cased letters in case the upper-cased
44 ones become unsupported! */
45 switch (letter)
46 {
47 case 'f':
48 case 'F':
49 return_value = 4;
50 break;
51
52 case 'd':
53 case 'D':
54 case 'g':
55 case 'G':
56 return_value = 8;
57 break;
58
59 case 'h':
60 case 'H':
61 return_value = 16;
62 break;
63
64 default:
65 return_value = 0;
66 break;
67 }
68
69 return return_value;
70 }
71
72 static const long mask[] =
73 {
74 0x00000000,
75 0x00000001,
76 0x00000003,
77 0x00000007,
78 0x0000000f,
79 0x0000001f,
80 0x0000003f,
81 0x0000007f,
82 0x000000ff,
83 0x000001ff,
84 0x000003ff,
85 0x000007ff,
86 0x00000fff,
87 0x00001fff,
88 0x00003fff,
89 0x00007fff,
90 0x0000ffff,
91 0x0001ffff,
92 0x0003ffff,
93 0x0007ffff,
94 0x000fffff,
95 0x001fffff,
96 0x003fffff,
97 0x007fffff,
98 0x00ffffff,
99 0x01ffffff,
100 0x03ffffff,
101 0x07ffffff,
102 0x0fffffff,
103 0x1fffffff,
104 0x3fffffff,
105 0x7fffffff,
106 0xffffffff
107 };
108
109
110 /* Shared between flonum_gen2vax and next_bits. */
111 static int bits_left_in_littlenum;
112 static LITTLENUM_TYPE *littlenum_pointer;
113 static LITTLENUM_TYPE *littlenum_end;
114
115 static int
next_bits(int number_of_bits)116 next_bits (int number_of_bits)
117 {
118 int return_value;
119
120 if (littlenum_pointer < littlenum_end)
121 return 0;
122 if (number_of_bits >= bits_left_in_littlenum)
123 {
124 return_value = mask[bits_left_in_littlenum] & *littlenum_pointer;
125 number_of_bits -= bits_left_in_littlenum;
126 return_value <<= number_of_bits;
127 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS - number_of_bits;
128 littlenum_pointer--;
129 if (littlenum_pointer >= littlenum_end)
130 return_value |= ((*littlenum_pointer) >> (bits_left_in_littlenum)) & mask[number_of_bits];
131 }
132 else
133 {
134 bits_left_in_littlenum -= number_of_bits;
135 return_value = mask[number_of_bits] & ((*littlenum_pointer) >> bits_left_in_littlenum);
136 }
137 return return_value;
138 }
139
140 static void
make_invalid_floating_point_number(LITTLENUM_TYPE * words)141 make_invalid_floating_point_number (LITTLENUM_TYPE *words)
142 {
143 *words = 0x8000; /* Floating Reserved Operand Code. */
144 }
145
146
147 static int /* 0 means letter is OK. */
what_kind_of_float(int letter,int * precisionP,long * exponent_bitsP)148 what_kind_of_float (int letter, /* In: lowercase please. What kind of float? */
149 int *precisionP, /* Number of 16-bit words in the float. */
150 long *exponent_bitsP) /* Number of exponent bits. */
151 {
152 int retval;
153
154 retval = 0;
155 switch (letter)
156 {
157 case 'f':
158 *precisionP = F_PRECISION;
159 *exponent_bitsP = 8;
160 break;
161
162 case 'd':
163 *precisionP = D_PRECISION;
164 *exponent_bitsP = 8;
165 break;
166
167 case 'g':
168 *precisionP = G_PRECISION;
169 *exponent_bitsP = 11;
170 break;
171
172 case 'h':
173 *precisionP = H_PRECISION;
174 *exponent_bitsP = 15;
175 break;
176
177 default:
178 retval = 69;
179 break;
180 }
181 return retval;
182 }
183
184 /* Warning: this returns 16-bit LITTLENUMs, because that is
185 what the VAX thinks in. It is up to the caller to figure
186 out any alignment problems and to conspire for the bytes/word
187 to be emitted in the right order. Bigendians beware! */
188
189 static char *
atof_vax(char * str,int what_kind,LITTLENUM_TYPE * words)190 atof_vax (char *str, /* Text to convert to binary. */
191 int what_kind, /* 'd', 'f', 'g', 'h' */
192 LITTLENUM_TYPE *words) /* Build the binary here. */
193 {
194 FLONUM_TYPE f;
195 LITTLENUM_TYPE bits[MAX_PRECISION + MAX_PRECISION + GUARD];
196 /* Extra bits for zeroed low-order bits.
197 The 1st MAX_PRECISION are zeroed,
198 the last contain flonum bits. */
199 char *return_value;
200 int precision; /* Number of 16-bit words in the format. */
201 long exponent_bits;
202
203 return_value = str;
204 f.low = bits + MAX_PRECISION;
205 f.high = NULL;
206 f.leader = NULL;
207 f.exponent = 0;
208 f.sign = '\0';
209
210 if (what_kind_of_float (what_kind, &precision, &exponent_bits))
211 {
212 return_value = NULL;
213 make_invalid_floating_point_number (words);
214 }
215
216 if (return_value)
217 {
218 memset (bits, '\0', sizeof (LITTLENUM_TYPE) * MAX_PRECISION);
219
220 /* Use more LittleNums than seems
221 necessary: the highest flonum may have
222 15 leading 0 bits, so could be useless. */
223 f.high = f.low + precision - 1 + GUARD;
224
225 if (atof_generic (&return_value, ".", "eE", &f))
226 {
227 make_invalid_floating_point_number (words);
228 return_value = NULL;
229 }
230 else if (flonum_gen2vax (what_kind, &f, words))
231 return_value = NULL;
232 }
233
234 return return_value;
235 }
236
237 /* In: a flonum, a vax floating point format.
238 Out: a vax floating-point bit pattern. */
239
240 int
flonum_gen2vax(int format_letter,FLONUM_TYPE * f,LITTLENUM_TYPE * words)241 flonum_gen2vax (int format_letter, /* One of 'd' 'f' 'g' 'h'. */
242 FLONUM_TYPE *f,
243 LITTLENUM_TYPE *words) /* Deliver answer here. */
244 {
245 LITTLENUM_TYPE *lp;
246 int precision;
247 long exponent_bits;
248 int return_value; /* 0 == OK. */
249
250 return_value = what_kind_of_float (format_letter, &precision, &exponent_bits);
251
252 if (return_value != 0)
253 make_invalid_floating_point_number (words);
254
255 else
256 {
257 if (f->low > f->leader)
258 /* 0.0e0 seen. */
259 memset (words, '\0', sizeof (LITTLENUM_TYPE) * precision);
260
261 else
262 {
263 long exponent_1;
264 long exponent_2;
265 long exponent_3;
266 long exponent_4;
267 int exponent_skippage;
268 LITTLENUM_TYPE word1;
269
270 if (f->sign != '-' && f->sign != '+')
271 {
272 if (f->sign == 0)
273 {
274 /* All NaNs are 0. */
275 memset (words, 0x00, sizeof (LITTLENUM_TYPE) * precision);
276 }
277 else if (f->sign == 'P')
278 {
279 /* Positive Infinity. */
280 memset (words, 0xff, sizeof (LITTLENUM_TYPE) * precision);
281 words[0] &= 0x7fff;
282 }
283 else if (f->sign == 'N')
284 {
285 /* Negative Infinity. */
286 memset (words, 0x00, sizeof (LITTLENUM_TYPE) * precision);
287 words[0] = 0x0080;
288 }
289 else
290 make_invalid_floating_point_number (words);
291 return return_value;
292 }
293
294 /* All vaxen floating_point formats (so far) have:
295 Bit 15 is sign bit.
296 Bits 14:n are excess-whatever exponent.
297 Bits n-1:0 (if any) are most significant bits of fraction.
298 Bits 15:0 of the next word are the next most significant bits.
299 And so on for each other word.
300
301 All this to be compatible with a KF11?? (Which is still faster
302 than lots of vaxen I can think of, but it also has higher
303 maintenance costs ... sigh).
304
305 So we need: number of bits of exponent, number of bits of
306 mantissa. */
307
308 bits_left_in_littlenum = LITTLENUM_NUMBER_OF_BITS;
309 littlenum_pointer = f->leader;
310 littlenum_end = f->low;
311 /* Seek (and forget) 1st significant bit. */
312 for (exponent_skippage = 0;
313 !next_bits (1);
314 exponent_skippage++);
315
316 exponent_1 = f->exponent + f->leader + 1 - f->low;
317 /* Radix LITTLENUM_RADIX, point just higher than f->leader. */
318 exponent_2 = exponent_1 * LITTLENUM_NUMBER_OF_BITS;
319 /* Radix 2. */
320 exponent_3 = exponent_2 - exponent_skippage;
321 /* Forget leading zeros, forget 1st bit. */
322 exponent_4 = exponent_3 + (1 << (exponent_bits - 1));
323 /* Offset exponent. */
324
325 if (exponent_4 & ~mask[exponent_bits])
326 {
327 /* Exponent overflow. Lose immediately. */
328 make_invalid_floating_point_number (words);
329
330 /* We leave return_value alone: admit we read the
331 number, but return a floating exception
332 because we can't encode the number. */
333 }
334 else
335 {
336 lp = words;
337
338 /* Word 1. Sign, exponent and perhaps high bits.
339 Assume 2's complement integers. */
340 word1 = (((exponent_4 & mask[exponent_bits]) << (15 - exponent_bits))
341 | ((f->sign == '+') ? 0 : 0x8000)
342 | next_bits (15 - exponent_bits));
343 *lp++ = word1;
344
345 /* The rest of the words are just mantissa bits. */
346 for (; lp < words + precision; lp++)
347 *lp = next_bits (LITTLENUM_NUMBER_OF_BITS);
348
349 if (next_bits (1))
350 {
351 /* Since the NEXT bit is a 1, round UP the mantissa.
352 The cunning design of these hidden-1 floats permits
353 us to let the mantissa overflow into the exponent, and
354 it 'does the right thing'. However, we lose if the
355 highest-order bit of the lowest-order word flips.
356 Is that clear? */
357 unsigned long carry;
358
359 /*
360 #if (sizeof(carry)) < ((sizeof(bits[0]) * BITS_PER_CHAR) + 2)
361 Please allow at least 1 more bit in carry than is in a LITTLENUM.
362 We need that extra bit to hold a carry during a LITTLENUM carry
363 propagation. Another extra bit (kept 0) will assure us that we
364 don't get a sticky sign bit after shifting right, and that
365 permits us to propagate the carry without any masking of bits.
366 #endif */
367 for (carry = 1, lp--;
368 carry && (lp >= words);
369 lp--)
370 {
371 carry = *lp + carry;
372 *lp = carry;
373 carry >>= LITTLENUM_NUMBER_OF_BITS;
374 }
375
376 if ((word1 ^ *words) & (1 << (LITTLENUM_NUMBER_OF_BITS - 1)))
377 {
378 make_invalid_floating_point_number (words);
379 /* We leave return_value alone: admit we read the
380 number, but return a floating exception
381 because we can't encode the number. */
382 }
383 }
384 }
385 }
386 }
387 return return_value;
388 }
389
390 /* JF this used to be in vax.c but this looks like a better place for it. */
391
392 /* In: input_line_pointer->the 1st character of a floating-point
393 number.
394 1 letter denoting the type of statement that wants a
395 binary floating point number returned.
396 Address of where to build floating point literal.
397 Assumed to be 'big enough'.
398 Address of where to return size of literal (in chars).
399
400 Out: Input_line_pointer->of next char after floating number.
401 Error message, or 0.
402 Floating point literal.
403 Number of chars we used for the literal. */
404
405 #define MAXIMUM_NUMBER_OF_LITTLENUMS 8 /* For .hfloats. */
406
407 const char *
vax_md_atof(int what_statement_type,char * literalP,int * sizeP)408 vax_md_atof (int what_statement_type,
409 char *literalP,
410 int *sizeP)
411 {
412 LITTLENUM_TYPE words[MAXIMUM_NUMBER_OF_LITTLENUMS];
413 char kind_of_float;
414 unsigned int number_of_chars;
415 LITTLENUM_TYPE *littlenumP;
416
417 switch (what_statement_type)
418 {
419 case 'F':
420 case 'f':
421 kind_of_float = 'f';
422 break;
423
424 case 'D':
425 case 'd':
426 kind_of_float = 'd';
427 break;
428
429 case 'g':
430 kind_of_float = 'g';
431 break;
432
433 case 'h':
434 kind_of_float = 'h';
435 break;
436
437 default:
438 kind_of_float = 0;
439 break;
440 };
441
442 if (kind_of_float)
443 {
444 LITTLENUM_TYPE *limit;
445
446 input_line_pointer = atof_vax (input_line_pointer,
447 kind_of_float,
448 words);
449 /* The atof_vax() builds up 16-bit numbers.
450 Since the assembler may not be running on
451 a little-endian machine, be very careful about
452 converting words to chars. */
453 number_of_chars = atof_vax_sizeof (kind_of_float);
454 know (number_of_chars <= MAXIMUM_NUMBER_OF_LITTLENUMS * sizeof (LITTLENUM_TYPE));
455 limit = words + (number_of_chars / sizeof (LITTLENUM_TYPE));
456 for (littlenumP = words; littlenumP < limit; littlenumP++)
457 {
458 md_number_to_chars (literalP, *littlenumP, sizeof (LITTLENUM_TYPE));
459 literalP += sizeof (LITTLENUM_TYPE);
460 };
461 }
462 else
463 number_of_chars = 0;
464
465 *sizeP = number_of_chars;
466 return kind_of_float ? NULL : _("Unrecognized or unsupported floating point constant");
467 }
468